Theo Demmers

Ammonia emission factors for UK agriculture

Ammonia (NH3) emission inventories are required for modelling atmospheric NH3 transport and estimating downwind deposition. A recent inventory for UK agriculture, estimating emission as 197 kt NH3–N yr−1, was constructed using 1993 statistical and census data for the UK. This paper describes the derivation of the UK-based emission factors used in the calculation of that emission for a range of livestock classes, farm practices and fertiliser applications to agricultural land. Some emission factors have been updated where more recent information has become available. Some of the largest emission factors derived for each farming practice include 16.9 g NH3–N dairy cow−1 d−1 for grazing, 148.8 g NH3–N liveweight unit−1 yr−1 for housed broilers and 4.8 g NH3–N m−2 d−1 for storage of solid pig and poultry waste as manure heaps. Emissions for land spreading of all livestock waste were 59% of the total ammoniacal nitrogen (TAN) applied as a high dry matter content slurry and 76% of TAN applied as farm yard manure. An updated estimate of emission from UK agriculture, using updated emission factors together with 1997 statistical and census data, is presented, giving a total of 226 kt NH3–N per year.

Dust in Pig Buildings

It is well documented in the international scientific literature that airborne dust in pig houses can cause serious health problems for humans as well as for animals. Extensive research has been carried out in different countries during the last few decades to improve the scientific understanding of air quality issues related to intensive animal production. Research and review papers were presented at the international symposium on Dust Control in Animal Production Facilities, held in Denmark in 1999. Different techniques have been used in order to reduce dust burdens in pig confinement buildings, but up to date only the procedure of spraying oil or a mixture of oil and water has contributed to reducing the indoor dust concentrations significantly. This article summarizes the current level of understanding of dust issues in intensive animal production buildings, mainly on the basis of papers presented at the above-mentioned symposium.

Controlled atmosphere stunning of broiler chickens. I. Effects on behaviour, physiology and meat quality in a pilot scale system at a processing plant

1. The effects of controlled atmosphere stunning on the behaviour, physiology and carcase and meat quality of broiler chickens were studied experimentally in a pilot scale plant. 2. Gas mixtures tested were: single phase anoxic mixture (90% Ar in air, <2% O2); single phase hypercapnic anoxic mixture (60% Ar, 30% CO2 in air, <2% O2); and biphasic hypercapnic hyperoxygenation mixture (anaesthetic phase, 40% CO2, 30% O2, 30% N2; euthanasia phase, 80% CO2, 5% O2, 15% N2). 3. Anoxic stunning resulted in the least respiratory disruption, mandibulation and motionlessness, but most head shaking, leg paddling and twitching. Loss of posture occurred soonest with hypercapnic anoxia with the earliest and most twitching and wing flapping in individuals and earliest leg paddling. Biphasic birds were most alert, exhibited most respiratory disruption and mandibulation, and had the latest loss of posture and fewest, but longest bouts of wing flapping and least leg paddling and twitching. 4. Significant and sudden bradycardia and arrhythmia were evident with all gas mixtures and were not related solely to anoxia or hypercapnia. Birds stunned by Ar anoxia showed a slightly more gradual decline from baseline rates, compared with hypercapnic mixtures. 5. Few differences were found between gas mixes in terms of carcase and meat quality. Initial bleeding rate was slowest in biphasic-stunned birds, but total blood loss was not affected. Acceleration of post-mortem metabolism in anoxic-stunned birds was not sufficient to allow de-boning within 5 h without the risk of tough meat. 6. On welfare grounds and taking into account other laboratory and field studies, a biphasic method (using consecutive phases of anaesthesia and euthanasia) of controlled atmosphere stunning of broilers is potentially more humane than anoxic or hypercapnic anoxic methods using argon or nitrogen.

Controlled atmosphere stunning of broiler chickens. II. Effects on behaviour, physiology and meat quality in a commercial processing plant

1. The effects of controlled atmosphere stunning on behavioural and physiological responses, and carcase and meat quality of broiler chickens were studied experimentally in a full scale processing plant. 2. The gas mixtures tested were a single phase hypercapnic anoxic mixture of 60% Ar and 30% CO2 in air with <2% O2, and a biphasic hypercapnic hyperoxygenation mixture, comprising an anaesthetic phase, 40% CO2, 30% O2, 30% N2, followed by an euthanasia phase, 80% CO2, 5% O2, 15% N2. 3. Birds stunned with Ar + CO2 were more often observed to flap their wings earlier, jump, paddle their legs, twitch and lie dorsally (rather than ventrally) than those stunned with CO2 + O2. These behaviours indicate a more agitated response with more severe convulsions during hypercapnic anoxia, thereby introducing greater potential for injury. 4. Heart rate during the first 100 s of gas stunning was similar for both gases, after which it remained constant at ≈230 beats/min for CO2 + O2 birds whereas it declined gently for Ar + CO2 birds. 5. In terms of carcase and meat quality, there appeared to be clear advantages to the processor in using CO2 + O2 rather than Ar + CO2 to stun broiler chickens, for example, a much smaller number of fractured wings (1·6 vs. 6·8%) with fewer haemorrhages of the fillet. 6. This study supports the conclusions of both laboratory and pilot scale experiments that controlled atmosphere stunning of broiler chickens based upon a biphasic hypercapnic hyperoxygenation approach has advantages, in terms of welfare and carcase and meat quality, over a single phase hypercapnic anoxic approach employing 60% Ar and 30% CO2 in air with <2% O2.

Production responses of weaned pigs after chronic exposure to airborne dust and ammonia

Nine hundred and sixty weaned pigs were exposed for 5·5 weeks to controlled concentrations of airborne dust and ammonia in a single, multi-factorial experiment. Production and health responses were measured but only the former are reported here. The treatments were a dust concentration of either 1·2, 2·7, 5·1 or 9·9 mg/m 3 (inhalable fraction) and an ammonia concentration of either 0·6, 10·0, 18·8 or 37·0 p. p. m., which are representative of commercial conditions. The experiment was carried out over 2·5 years and pigs were used in eight batches, each comprising five lots of 24 pigs. Each treatment combination was replicated once and an additional control lot (nominally ≈ 0 mg/m 3 dust and ≈ 0 p. p. m. ammonia) was included in each batch to provide a baseline. The dust concentration was common across the other four lots in each batch in which all four ammonia concentrations were used; thus the split-plot design was more sensitive to the effects of ammonia than dust. The pigs were kept separately in five rooms in a purpose-built facility. The pollutants were injected continuously into the air supply. Ammonia was supplied from a pressurized cylinder and its concentration was measured with an NO x chemiluminescent gas analyser after catalytic conversion. The endogenous dust in each room was supplemented by an artificial dust, which was manufactured from food, barley straw and faeces, mixed by weight in the proportions 0·5: 0·1: 0·4. The ingredients were oven-dried, milled and mixed and this artificial dust was then resuspended in the supply air. Dust concentration was monitored continuously with a tribo-electric sensor and measured continually with an aerodynamic particle sizer and gravimetric samplers. Live weight per pig and cumulative food intake per pen of 12 pigs were measured after 5·5 weeks of exposure. Exposure to both aerial pollutants depressed live weight relative to the control (control v. pollutant, 25·7 v. 25·0 (s.e.d. = 0·33) kg, P = 0·043) and there was a trend for food intake to be lower for pollutant-exposed pigs (control v. pollutant 292 v. 280 (s.e.d. = 7·1) kg per pen, P = 0·124). The reduction in live weight and food intake was dependent upon the concentration of dust (mean across all ammonia concentrations for increasing dust concentration; live weight 25·3, 26·4, 24·0 and 24·5 (s.e.d. = 0·65) kg, P = 0·081; food intake 295, 316, 248 and 263 (s.e.d. = 14·3) kg per pen, P = 0·016) but not ammonia (mean across all dust concentrations for increasing ammonia concentration; live weight 24·4, 25·1, 25·3 and 25·3 (s.e.d. = 0·41) kg, P = 0·158; food intake 279, 275, 288 and 279 kg (s.e.d. = 9·0) kg per pen, P = 0·520). There was an interaction between dust and ammonia for live weight (P = 0·030) but the effects were complicated and may have been the result of a type I error. There was no interaction for food intake (P = 0·210). In general, both food intake and live-weight gain, but not food conversion efficiency, were lower for weaned pigs exposed to 5·1 and 9·9 mg/m 3 dust concentrations compared with 1·2 and 2·7 mg/m 3 treatments. Other measures of production were also analysed and supported the overall interpretation that dust concentrations of 5·1 mg/m 3 and higher depress performance. This study is the first to quantify the effects of chronic exposure to common aerial pollutants on the performance of weaned pigs. The results suggest that dust concentrations of 5·1 or 9·9 mg/m 3 (inhalable fraction) across ammonia concentrations up to 37 p.p.m. adversely affect performance. The commercial significance of these findings depends on the financial benefits of the superior production at low dust concentrations relative to the cost of providing air of this quality.

An assessment of ways to abate ammonia emissions from UK livestock buildings and waste stores. Part 1: ranking exercise

Abstract The options for abating ammonia emissions from livestock buildings and waste stores under UK conditions have been assessed. There is increasing interest in reducing such emissions, which contribute to long-range atmospheric pollution problems, and which, via subsequent deposition, can also harm sensitive ecosystems. A literature review was first carried out, and a “brainstorm” idea-generating session was held, together leading to lists of feasible abatement approaches: one for each of a range of types of livestock buildings and waste stores. A ranking exercise was then conducted. A set of aspects of each application of each feasible abatement approach was drawn up: the aspects considered included not only capital costs and running costs but also such others as animal welfare, stage of development and knock-on effects. Each aspect of each application of each approach was given a ranking of between 1 (very poor) and 5 (very good). When the aspects of “potential abatement” and “achievable abatement now”, as well as either “capital costs” or “animal welfare”, were weighted by a factor of 5, the “best bet” abatement approaches for livestock buildings were identified as (a) dietary manipulation (for all types), (b) raising the C/N ratio by generous use of bedding (for any buildings based on solid manure), (c) exhaust air cleaning, especially by bioscrubbers (for force-ventilated pig and poultry buildings), (d) oil layers or (e) fixing with acid (for slurry-based piggeries) and (f) drying by ventilation of muck (for any poultry building). For waste stores, the “best bet” abatement approaches were identified as (g) replacing storage with industrial scale processing or (h) with land filling (niche solutions only), (i) dietary manipulation, (j) fixing with acid (slurries only), (k) increasing the surfaces resistance to ammonia volatilisation (by crusts for cattle slurry, but by floating granules for pig slurry), (l) minimising surface area by heap shape (solid manures), and (m) cover sheets (solid manures). For stored poultry manure, the low moisture content allowed good showings by the additional options of (n) drying, and, in the case of poultry manure with litter in certain parts of the UK, (p) sale for combustion in a Non-Fossil Fuel Obligation (NOFFO) power station, the electricity from which commands a higher price than that from a conventional power station. A closer look at the economic consequences of different abatement approaches was taken by means of a mathematical model: this work is reported in a companion paper.

Embryonic development and the physiological factors that coordinate hatching in domestic chickens

Embryonic growth and development is influenced by both endogenous and exogenous factors. The purpose of this review is to discuss the critical stages of chick embryonic development in relation to functional maturation of numerous organ systems, the acquisition of thermoregulation, and the hatching process. In addition, the mechanism of hatching, including sound synchronization and hormonal and environmental stimulation, will be discussed. Finally, the importance of effective hatching synchronization mechanisms will also be highlighted.

Response characteristics of nasal trigeminal nociceptors in Gallus domesticus

Although the chemoreceptive properties of the nasal trigeminal system are well known, the physiological characteristics of nasal nociceptors responding to both mechanical and chemical stimulation have not been well described. In this study, the activity of single nasal trigeminal units recorded from microdissected twigs of the ethmoidal nerve of anaesthetized hens (Gallus domesticus) was investigated. Using a mechanical search stimulus, 20 slowly and 22 rapidly adapting nasal mechanoreceptors were identified, exhibiting mean thresholds of 2.96 g. Twelve slowly adapting units also exhibited chemical sensitivity when exposed to ammonia gas. These had mean response thresholds of 0.232% vapour saturation and exhibited variable stimulus-response profiles. This is the first study to quantify the responses of polymodal nasal nociceptors to a noxious airborne chemical in any species.

Physiological responses of laying hens during whole-house killing with carbon dioxide

1. Poultry on farms are sometimes required to be killed in an emergency, such as during a disease epidemic, yet none of the available methods are ideal. Whole-house carbon dioxide (CO2) administration has practical advantages, but gives rise to welfare concerns. 2. The study measured the body temperature, respiration, cardiac and brain activity (EEG) responses of 10 adult hens placed in tiered cages in a deep pit house while the entire flock (28,000 end-of-lay hens) was killed with CO2. Video and thermographic images were also recorded. Liquid CO2 was injected into the building producing a gaseous concentration of 45% within 19 min. 3. Those hens nearest the gas delivery site showed delayed respiratory, cardiac and EEG responses compared with those at more distant locations. Although sub-zero temperatures were recorded in the immediate vicinity of some birds, body temperatures indicated that they did not die of hypothermia. 4. EEG characteristics strongly associated with unconsciousness were used to determine an unequivocal time to loss of consciousness; this ranged from 6·0 to 10·5 (average 7·8) min after onset of gas injection. Distinctive cardiac and respiratory responses were seen following gas exposure; in particular, birds responded to inhalation of CO2 by deep breathing. 5. The primary welfare concern is the duration of unpleasant respiratory effects, such as deep breathing, while the birds were substantively conscious. However, the concentration of CO2 to which the birds were exposed while conscious would not have stimulated nasal and oral nociceptors. Time to death varied between 12·0 and 22·1 min after gas delivery.

The relationship between physical activity and leg health in the broiler chicken

1. The relationship between the physical activity and leg health of broiler chickens was assessed on a semi-commercial scale. 2. Three batches of birds (2128 per batch) were raised under two lighting regimes during the photoperiod; either a step-wise change of light intensity alternating between an illuminance of 200 and 10 lx or a constant illuminance of 10 lx. The activity of focal individuals (24 per batch) was observed at 2, 4 and 6 weeks of age, and leg health assessed weekly, based on gait score, the prevalence of burns on the hock and foot pad, and angulation and rotation of the leg at the intertarsal joint. Cortical bone density and thickness and area moments of inertia of the mid-physis tibiotarsus were measured post mortem at 6 weeks of age. 3. The step-wise change in light intensity did not affect overall performance, activity or leg health. 4. An individual birds activity did not affect its gait score, the prevalence of hock burn or foot pad burn, cortical density or thickness or shape of the tibiotarsus. Sex of the bird was the only factor to affect significantly the area moment of inertia in the horizontal and vertical planes of the tibiotarsus, with females showing a lower moment of inertia for both. No variable had a significant effect on cortical density or thickness. Mean cortical density was low across all birds and may indicate that, when allowed to move freely as much or as little as they choose, broiler chickens do not exercise enough or do not perform the higher impact activities required to affect bone quality. 5. These findings imply that the activity of broiler chickens raised on a semi-commercial scale is unaffected by step-wise changes in light intensity and that other husbandry measures are needed to raise activity and hence improve leg health.